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    <title>Document</title>
    <style>
        /* strong span a em  b i u 行内元素 */
        /* 一行可以放多个 */
        /* 设置宽度和高度无效 */
        /* 宽度和高度根据自己的内容撑开 */
        span{
            width: 500px;
            height: 500px;
            background-color: pink;
        }
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<body>
    <span>a231</span>
    <span>acd</span>
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